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Question: short cranks
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I've been thinking about getting some shorter (read: 165-170 mm for a 56 frame) cranks for my tri bike and I was wondering if anybody had any particularly good or bad opinions of shorter cranks. I've been doing some reading on why they're trending and supposedly beneficial, but I feel like getting the opinions of actual cyclists and triathletes is the best way to go.

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Re: Question: short cranks [Red X] [ In reply to ]
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The current Shimano 4 arm cranks are well reviewed. I have the 5800 crank on my tri bike and am really happy with it.

If you're going shorter on your cranks then will will also want to consider going for slightly smaller chainrings too:
http://www.slowtwitch.com/...nd_Gearing_4095.html
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Re: Question: short cranks [Liaman] [ In reply to ]
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I should also mention that I need them to be BB30 compatible. I know there are adapters available for many different brands, but is it worth getting the adapter for, say, a 105 crankset? (Or other non-compatible brand)

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Re: Question: short cranks [Liaman] [ In reply to ]
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unless you want the equivalent of larger rings without anyone commenting on that fact ;) stealth rings as it were, helps to hit 50+mph on downhills where coasting wont cut it :)-
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Re: Question: short cranks [Red X] [ In reply to ]
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I'm 5'9" and 28M running 148mm cranks on a 54cm S Works Transition. Sometimes I run the straight seat post giving me an effective TT length of 50cm and sometimes I run the team setback giving me 53cm effective TT length. I have a 30.5" inseam. I run a 48/39 with 12-28 on most race days, 11-26 on flat courses.

I've been through 2 partial ACL tears, 1 MCL tear, and an arthroscopy to remove cartilage, all in my left knee. Between ages 16 and 22 I was in 6 car accidents, 1 head-on and 5 times rear ended, with the most serious being hit by a car doing ~70mph while we had slowed down to 30mph because of traffic. I had another similar accident going ~25mph and hit from behind by a car doing ~45mph. Both sucked.

As a result, I have limited hip and knee mobility. There is rubbing in my knee joint and it generates more heat the further I bend it. Applying load at the top of my power stroke with a typical 170mm crank length generates a level of pain and discomfort I can only bear for a sprint race. As such, I had Mark at Bikesmith Design tap me a set of SRAM Apex cranks at 148mm. This allows me to place my saddle higher and put less stress on my knees and hips as the circle I make around the BB is smaller. The obvious requirement here is that my cadence has to go up.

It's not for everyone. You have to have the engine to sustain a higher HR on the bike and go even higher on the run. I believe the numbers I have say that I jumped around 10-12bpm average making the switch but that includes a cadence jump from ~80rpm to 95-110rpm. I couldn't hit 110rpm with 170mm cranks on my best day since I have two broken ribs on my left side that healed incorrectly and my left knee hits them in aero with the long cranks.

148mm is a compromise for me. You lose a LOT of leverage with short cranks. I can't climb nearly as well as I could before and I have completely lost my climbing fitness over the last couple years I've run these cranks.

In my opinion, you're not going to see much of a difference in a 5mm shift but you might in going to 165mm, which I assume is a 10mm drop for you. You've given nothing about your actual body dimensions so I've simply given you my background, why I made the choice, and what it does for me. Feel free to PM or ask questions here if you want.
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Re: Question: short cranks [jeffp] [ In reply to ]
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jeffp wrote:
unless you want the equivalent of larger rings without anyone commenting on that fact ;) stealth rings as it were, helps to hit 50+mph on downhills where coasting wont cut it :)-

Haha yes, I hadn't considered that!
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Re: Question: short cranks [Red X] [ In reply to ]
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I've got no experience with BB adaptors, so I'm hesitant to say either way.
FSA do some decent BB30 compatible cranks. Although I don't know enough to do side by side comparisons with the Shimano stuff, I suspect that the Shimano 4 arm cranks will be better.
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Re: Question: short cranks [soobrex1] [ In reply to ]
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I'm about 6'1" with a 32 inseam. The cranks on the size 56 B14 are 170mm, meaning there would only be a difference of 5mm if I went down to 165mm. Looks like the only compatible 160mm options are offered by Lightning and ROTOR. Aside from knee comfort, is there much of a difference in efficiency or feeling on the run from using shorter cranks? I've read up a bit on it, but I haven't found many personal opinions or accounts.

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Re: Question: short cranks [Red X] [ In reply to ]
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It's a question of fit. If shorter cranks help you achieve better/more comfortable fit, then that's a good reason. But don't go looking for some magical power gain.

Search this forum for the term "Crank Length" and you will find a wealth of discussion on the topic.
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Re: Question: short cranks [Red X] [ In reply to ]
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This is something that was brought up in the powercranks thread. What is the right crank length to inseam ratio? There is obviously a sweet spot in height for the 170-175mm cranks that get shipped out on bikes (with 165mm starting to get shipped now). At what height are you too tall for 175 and need to go 180? At what height do you need shorter cranks? Because fit is so individual, it's really hard to do something like this. Even if fitters got together and succeeded with a straight ratio or a more complicated algorithm, it would only be a starting point and would need tweaking for each individual rider.

I feel more efficient on the run because I'm not hitting some of the same muscles I do with longer crank arms and my hips are not as tight.
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Re: Question: short cranks [soobrex1] [ In reply to ]
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People keep over thinking crank length.




Last edited by: Nick B: Apr 27, 15 10:03
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Re: Question: short cranks [Nick B] [ In reply to ]
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I know they do. That's why I mentioned a more complicated algorithm. I can't hit my custom fit position on cranks longer than 155mm because my knee hits my ribs. Changing the crank arm length would require me to change my saddle height, fore/aft position, and saddle/aerobar drop. It changes everything about how I ride.

On a hilly course, I would ask "what is the longest crank arm I can ride and still hit my ideal position" whereas on a flatter course I would ask "what is the crank arm length that lets me hit my ideal cadence and position."
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Re: Question: short cranks [Red X] [ In reply to ]
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My experience was a home run. My goal was simply better fit and it did that in spades. I'm 6'1" 35 1/2 inseam and worked my way down to 165's. The very odd thing for me was coming down from 175 to 165 wasn't a linear increase in drop for me. It opened a few other 'can's of worms' in that I wanted to ride a little steeper, but the little bit of hip angle clearance ended up having me go from ~ 11cm of drop to 16.5cm. YMMV, but my PT said I was within 5 watts of the 175's from the first ride with 165's. Difference was I was WAY more aero and WAY more comfy so a huge win for me.

Good luck!
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Re: Question: short cranks [soobrex1] [ In reply to ]
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soobrex1 wrote:
I know they do. That's why I mentioned a more complicated algorithm. I can't hit my custom fit position on cranks longer than 155mm because my knee hits my ribs. Changing the crank arm length would require me to change my saddle height, fore/aft position, and saddle/aerobar drop. It changes everything about how I ride.

On a hilly course, I would ask "what is the longest crank arm I can ride and still hit my ideal position" whereas on a flatter course I would ask "what is the crank arm length that lets me hit my ideal cadence and position."

I love my 200 cranks. All this stuff about drop is way over rated. If one does lots of hilly races like I do, not much time is in the aero position anyways.

Not everyone rides or like shorter cranks. Give them all a try and find what is best for you, just like bike fit, more than one way to do it.

Dave Campbell | Facebook | @DaveECampbell | h2ofun@h2ofun.net

Boom Nutrition code 19F4Y3 $5 off 24 pack box | Bionic Runner | PowerCranks | Velotron | Spruzzamist

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Re: Question: short cranks [soobrex1] [ In reply to ]
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The only one who seems to understand cranks is Dev who is short and rides on 170's which he feels is a "long" crank for his height. If short folks want to try to understand what if feels like for
a tall person to ride 170's, try riding 145's or even 140's and come back with how it feels.

Dave Campbell | Facebook | @DaveECampbell | h2ofun@h2ofun.net

Boom Nutrition code 19F4Y3 $5 off 24 pack box | Bionic Runner | PowerCranks | Velotron | Spruzzamist

Lions don't lose sleep worrying about the sheep
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Re: Question: short cranks [h2ofun] [ In reply to ]
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I hear you. Mark told me his fastest triathlete was on 130's. I'm thinking about going to 130-135 from 148 and running something like 34/46 up front to see how that works for me. On dead flat courses I'd probably run an 11-21 and leave the 12-28 for hilly courses.

You really feel it out of the saddle. The circles I make on 148 feels small, can't wait to see what smaller cranks feel like.
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